The present invention relates to a data transmission system for an entrance intercom and security monitoring system in a home automation (HA) system using a data transfer bus inside the home.
Conventional entrance intercom and securitY systems are described below with reference to FIGS. 1-3.
In FIG. 1, the output of camera 51 installed in the entrance is connected to the input of inside unit 52 by a dedicated line. A TV modulator 53 is provided in inside unit 52 to modulate the camera output (television signal) for output to the specified television channel, channel 1 (CH1) or channel 2 (CH2). Either the broadcast signal from the antenna or the output signal from TV modulator 53 is then input to television set 55 via a switch (SW) 54.
With the construction shown in FIG. 1, the switch 54 is normally switched to the antenna so that normal television broadcasts can be viewed on the television set. When a call is received from either intercom 56 or 57, the user switches switch 54 to the TV modulator 53 side, resets the television set 55 channel selector to either CH1 or CH2 depending on the modulator connection, and is then able to view a visitor picked up by camera 51 on the screen of television set 55 while talking with the visitor through intercom 56, 57.
An alternative conventional system is shown in FIG. 2. This system differs from that shown in FIG. 1 in that the output signal of TV modulator 53 in inside unit 52a is converted to a signal on an unused channel in the UHF or VHF band and carried with the other TV signals from the antenna by a mixer 58.
With this system, the channel selector of television set 55 is set to a normal broadcast channel for program viewing. When a visitor comes, the user simply selects the preset UHF channel to monitor the output of camera 51. The systems in both FIG. 1 and FIG. 2 can also be used to constantly monitor the entrance even when a visitor is not present.
In FIG. 3 is shown a system using a two-way line 60 and a bidirectional branch junction 61. When a visitor comes, the detection signal output from a visitor detection circuit 62 is sent over the two-way line 60 through a modem 63 and a mixer 64, branched by a bidirectional branch junction 61 for relay to control a circuit 73 via a mixer 74 and a modem 72, thus notifying the occupant inside that a visitor has come to the entrance.
The signal output from the camera 66 and microphone 67 installed in the entrance is modulated to a specific television frequency by a television modulator 65. The modulated signal is output to the indoor side through the mixer 64 and two-way line 60, and input to a television demodulator 75 through a mixer 74 for demodulation of the video and audio signals. The video signal carries the image of the visitor taken by the monitor camera for playback on the dedicated monitor television 76, and the audio signal carries the voice of the visitor for reproduction via a speaker 71 in a handset 70.
Similarly, the audio from inside the room is converted to an audio signal by a microphone 77 also provided in the handset 70, modulated to a specific frequency by an audio transmission circuit 78, and input to the bidirectional branch junction 61 via the mixer 74. The signal is input by the two-way line 60 to the mixer 64 on the entrance side where it is received by an audio receiving circuit 68 and amplified through a speaker 69 so that the voice from the party inside can be heard by the visitor outside.
However, a conventional system configured as described above presents the following problems.
Specifically, with the system as shown in FIGS. 1 and 2, when the inside party learns via the intercom that a visitor has come, the inside party must reset the switch 54 and tune television set 55 to the proper channel if the visitor is to be viewed on the television. With the system as shown in FIG. 3, the dedicated monitor television 76 is required for viewing visitors; this dedicated monitor is incapable of receiving conventional television broadcasts, and if only one monitor television 76 is provided, the visitor can only be monitored in that single location where the monitor is installed. Monitoring the video from the entrance camera at multiple locations requires the installation of multiple monitor televisions 76, resulting in a corresponding increase in cost. In addition, this monitor television 76 must remain with the power normally on to monitor the visitors at the entrance.
The camera monitoring sub-system of a conventional home automation system is described below with reference to FIGS. 4 to 6.
FIG. 4 shows the configuration of a conventional camera monitoring system, wherein a reference numeral 80 is a monitor camera, 82 is a dedicated cable used to carry the image (video signal) from the monitor camera 80, and 81 is a monitor television which displays the image received from monitor camera 80. The operation of this camera monitoring system is described below. The image captured by monitor camera 80 is transferred over a cable 82 and displayed on the dedicated monitor television 81. With this system there is only one monitor camera 80, and a dedicated monitor television and cable are required.
FIG. 5 shows the configuration of a system using multiple monitor cameras, wherein a reference numerals 80a to 80c indicate the monitor cameras, 83 is a sequential switch used to control these multiple monitor cameras 80a-80c, and 81 is the monitor television used to view the image from the monitor camera selected by a sequential switch 83. Multiple monitor cameras can be connected in this system, but as in the system shown in FIG. 4, a dedicated monitor television and cable are required.
FIG. 6 shows a system which uses an existing, conventional television receiver and multiple monitor cameras configured so that the image from the monitor is displayed on the conventional television. In these FIGS. 80a-80c are monitor cameras, 82 is a dedicated cable used to carry the video signal from monitor cameras 80a-80c, 83a to 83c are modulators which convert the video image from monitor cameras 80a-80c to a specific broadcast signal wave, and 84 is a mixer which mixes the images from monitor cameras 80a-80c for relay to a television receiver 85. While this system makes it possible to use an existing television monitor, it is still necessary to tune the television to the channel used for monitoring camera signal reception, and dedicated cables are still needed.